When oil is present in subterranean rock formations such as sandstone, carbonate, or shale, the oil can generally be exploited by drilling a borehole into the oil-bearing formation and allowing existing pressure gradients to force the oil up the borehole. This process is known as primary recovery. If and when the pressure gradients are insufficient to produce oil at the desired rate, it is customary to carry out an improved recovery method to recover additional oil. This process is known as secondary recovery. Primary oil recovery followed by secondary oil recovery, such as injection of water or gas to force out additional oil, are able to remove generally around 30 percent of the total oil content of an oil reservoir in many fields.
In waterflooding, pressurized water is injected into the oil-bearing formation after primary recovery and produced from neighboring hydrocarbon production wells. First hydrocarbon, and subsequently hydrocarbon and water are recovered from the production well.
Even after secondary recovery such as waterflooding, large amounts of the original oil remain in place. The fraction of unrecoverable hydrocarbon is typically highest for heavy oils, tar, and complex formations. In large oil fields, more than a billion barrels of oil can be left after conventional waterflooding. In addition to waterflooding, carbon-dioxide-miscible flood projects are also used. Tertiary recovery then becomes the focus. It is estimated that current tertiary oil recovery techniques have the ability to remove an additional 5 to 20 percent of the oil remaining in the reservoir. Given the current world dependence on fossil hydrocarbons, the development of effective tertiary oil recovery strategies for higher oil recovery promises to have a significant economic impact. Current methods of tertiary recover are effective, but expensive. Current tertiary methods still leave significant amounts of original oil in place in the field.
Much of the remaining oil in place after primary and secondary recovery is in micro-traps due to capillary forces or adsorbed onto mineral surfaces through irreducible oil saturation as well as bypassed oil within the rock formation. Encouraging movement of normally immobile residual oil or other hydrocarbon is commonly termed tertiary recovery. It is known to use microorganisms such as bacteria to dislodge the oil in micro-traps or adsorbed onto mineral surfaces to recover additional oil during the waterflooding phase. This typically involves the introduction of a microorganism from outside. These microbes create methane, which is then recovered.
It is also known that polymers and gelled or crosslinked water-soluble polymers are useful in enhanced oil recovery and other oil field operations. They have been used to alter the permeability of underground formations in order to enhance the effectiveness of water flooding operations. Generally, polymers or polymers along with a gelling agent such as an appropriate crosslinking agent in a liquid are injected into the formation. Both microbe-based and polymer-based enhanced recovery are expensive processes.
The diagenetic fabrics and porosity types found in various hydrocarbon-bearing rocks can indicate reservoir flow capacity, storage capacity and potential for water or CO2 flooding. The goal is to force oil out of high-storage-capacity but low-recovery units into a higher recovery unit. This allows an increase of recovery of oil over predicted primary depletion recovery such that a higher percentage of the original oil in place is recovered.
Traditional tertiary recovery operations include injection of the CO2 or water into the well. There is a need for an improved composition for enhanced oil recovery. It would be advantageous to use commercially available traditional injection facilities to reduce capital expenditures.
To fully capitalize on their national resources, oil-producing countries must enhance domestic petroleum production through the use of advanced-oil recovery technology. Operating companies, typically conservative in stating recoverable reserves, have a need to increase recoverable reserves from proven reserves as opposed to development of unproven reserves. There is a need for cost effective oil recovery techniques to maximize removal of original oil in place per field. There is a need for a cost effective oil recovery technique to reduce development costs by more closely delineating minimum field size and other parameters necessary to successfully recover oil. There is a need for tertiary recovery that can utilize simple or current application procedures.
U.S. Pat. No. 6,225,263 teaches a method of increasing the recovery of oil and/or gas from an underground formation by injecting into the formation an aqueous solution of a mono alkyl ether of polyethylene glycol.
U.S. Pat. No. 3,902,557 describes a method of treating the formation surrounding a well by injection of a solvent including a C4 to C10 alkyl ether of a polyglycol ether containing a C4 to C10 alkyl ether of a polyglycol ether containing 10-22 carbon atoms per molecule. C4 to C8 monoalkyl ethers of tri and tetra ethylene glycols are preferred in particular the hexyl ether while the butyl ether is also mentioned. The solvent may be diluted with an organic liquid such as alcohol, e.g. isopropanol.
FR Patent No 2735524 is directed toward a method of secondary and tertiary recovery through the use of alcohol in an amount of 1 to 5% by weight to solvate asphaltenes.
A need exists for a cost effective composition and method of use of the composition to improve enhanced oil recovery. There is a need to capitalize on the original oil in place that is unrecovered by primary and/or secondary recovery method.